The spacecraft could then gather samples from these rocks to determine what theyвЂ™re made of. Overall, the idea is to send the Comet Hitchhiker to as many small bodies as possible throughout our cosmic neighborhood. The tethers would also need to be between 62 and 620 miles long for the maneuver to work. Zylon and Kevlar could work, but the engineers are also considering more advanced technologies like a carbon nanotube tether with a diamond harpoon - incredibly strong materials. Masahiro Ono, the principal investigator based at JPL, says the spacecraft's tethers will have to be made of super strong material. When it does, the probe will reel in its tethers very slowly in order to land. (Fishermen also do this when they hook big prizes, so their line doesn't snap right away from too much force.) Eventually the spacecraft will match the velocity of the asteroid. The vehicle will then extend the tethers a bit so there isn't too much tension on the rope. When the spacecraft meets up with an asteroid, it will cast out its line harpoons will shoot out tethers to connect the spacecraft to the rock. The hitchhiking idea would get rid of the need for fuel during the landing process, JPL says. This braking process requires a lot of propellant. Asteroids and comets are pretty small too, with low gravitational pulls, so the spacecraft has to do most of the work to land. Then if it does reach the asteroid, the vehicle has to slow down to match the object's speed. So a spacecraft has to be much faster than an asteroid to catch up.

Right now, landing objects on asteroids is tough since these rocks move at a speed of about 15 miles per second. The idea was dreamed up by NASA's Jet Propulsion Laboratory as a way of using less fuel to land spacecraft on these space rocks. Once the vehicle finishes a ride with one asteroid, it will disconnect and hitch a ride with another. The idea is to make a probe - called Comet Hitchhiker - that would 'catch rides' on asteroids by spearing them with tethers. NASA engineers say they have come up with an easier way of exploring comets and asteroids in our Solar System: harpooning fast-moving space rocks.

Space engineers can you move asteroids